Burner control apparatus



July 19, 1960 N. SEEGERT BURNER CONTROL APPARATUS Filed Feb. 24, 1956 illll lllllllllllflllllllllllllllllilllhll1 WWW INVENTOR- egyaff Neal 3 B Y BURNER CONTROL APPARATUS Neal Seegert, Elm Grove, Wis., assignor to Baso, Inc., Milwaukee, Wis., a corporation of Wisconsin Filed Feb. 24, 1956, Ser. No. 567,593

7 Claims. (Cl. 67--2.1)

This invention rel-ates in general to thermoelectn'eally powered burner control apparatus and more particularly to a system having thermoelectrically powered time controlling means therein.

. -In the control of fluid fuel burners for incinerators or the like, it has long been desired to have a simple timing mechanism to shut olf the burner after it has been in operation for predetermined length of time. Prior art devices using spring wound mechanisms have various disadvantages including the fatigue of the power mechanisms after extended use thereof. Electrical timing devices, on the other hand, have heretofore required the use of ,outside separate power sources with the attendant installation and service problems. i

. It is the general object of the present invention to pro-' vide a fluid fuel control apparatus having a simple rugged timing mechanism coacting with flow control means, both of which are powered by energy derived from the buming of the fluid fuel which they control.

Another object of the present invention is to provide a device of the aforementioned general characteristics utilizing a single flow control means with holding means therefor, said holding means being operable when energized. to

hold said flow control means in flow-permitting position,

said holding means being operable when deenergized to allow biasing means to position said flow control means in flow-preventing position responsive to both pilot burner outage and timing means associated with said flow control means and thus the device provides safe time controlled fluid flow.

Another object of the present invention is to provide a device of the aforementioned characteristics with an elect-roresponsive holding means energizable by thermoelectric generator means, the latter means also being operable to energize theaforementioned timing means.

Another object of the present invention is to provide the above described device with circuit controlling means in circuit with said holding means, said circuit controlling means being movable between circuit interrupting and- V circuit completing positions by the aforementioned automatic timing means and also by a manual setting means.

Another object of the present invention is to provide a device as above characterized with unitary reset and time setting means operable to reset the flow control means to flow-permitting position said setting means also being operable to position the timing means so as to maintain said flow control means in said flow-permitting position for a predetermined desired period of time.

vThe novel'features that are characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantagesthereof will best be understood by the following description of a specific embodiment when read in connection with the accom ment of the burner control apparatus, portions of said sys- Patented July 19, 1960 tem and the electrical circuitry thereof being shown semidiagrammatically; and

Figure 2 is a fragmentary view of a portion of the same embodiment taken along lines 2-2 of Figure 1.

Referring now to the drawings, Figure 1 shows a system for controlling the flow of fluid fuel to main and pilot burners 8 and 12 comprising a burner control apparatus 9 interposed in a fuel supply line 16 and operable to maintain said fuel flow for predetermined desired periods of time alter ignition of the burners whereupon the device 9 automatically shuts down the entire fuel flow to both burners. The apparatus comprises an arrangement of reset-timeset means 41 which is operable to reset and cock the device 9 and to adjustably determine or set the period of time the first or flow control means 14 will be retained in flow-permitting position by suitable holding or operator means such as shown at 22. Automatic timed operation of the system is accomplished by controlling the state of energization of the circuit to the holding or operator means 22 with suitable control means,

' for example circuit controlling means such as shown at 24, the latter being automatically actuated between circuit interrupting and circuit completing positions by an oscillating constant speed driving means as shown generally at 30. The device 9 will now be explained in detail.

The direct control of the fluid fuel, for example gaseous fuel, may be provided by suitable control means 14 which in the illustrated embodiment comprises a valve disc 13 which is interposed between a fuel inlet 16a and' a plurality of fuel outlets such as 17a and 18a formed in the casing 10. The disc 13 is cooperable with a valve seat 15, seating of disc 13 preventing all fuel flow to the main burner 8 and the pilot burner 12 through their respective supply pipes 18 and 17, the disc 13, when moved to a position spaced away from seat 15, permitting fuel to flow to both burners.

Condition responsive holding means 22 may be mounted on the upstream side ofrvalve seat 15 and is operable when energized for retaining the valve disc 13 in flow-permitting position. The holding means 22 may be of any suitable or desired type and is here comprised of a generally cylindrical hood or casing 31. Fixed within the hood 31 is an electromagnet 35 having an energizing coil or winding 36 thereon, one end of which is grounded at 54 the other end of which may be connected in circuit with a thermoelectric generator 20 through conductors 21a and 21.

An armature 37 is cooperable with the electromagnet 35 and is carried by an axially slidable stem 38 which projects through a suitable bearing in an end wall of the hood 31 and has the valve disc 13 mounted on the exterior end thereof. A coiled compression spring 39 surrounds the stem 38 between the hood 31 and the valve disc 13 and biases the armature 37 away from the pole faces of the electromagnet 35 and the valve disc 13 toward engagement with valve seat 15. The electromagnet 35 when energized is adapted to hold the armature 37 and the valve disc 13 in the cocked flow-permitting position shown when said parts are moved to this position against the bias of the spring 39. It is to be noted that the electromagnet 35 has insufficient attractive power when energized to move or attract the armature from a retracted position, but it does have sufiicient power to hold or retain the parts when moved thereto by some outside means such as the reset timeset means 41.

Means for deenergizing the electromagnet 35 to thereby cause armature 37 to release and the cooked valve disc 13 to seat may be provided by the circuit controlling or switch means 24 which is interposed in circuit between the ground 54 and the generator 20 and is here shown semi-diagrammatical1y.- The circuit controlling means 24 may be of any suitable or desired type, the preferred,

form being an expansible and contractible bellows 47 enclosing a pair of cooperating control members, for example contacts 48 and 49 suitably attached to the end walls 49a and 48a of said bellows for actuation thereby. As here shown the contacts may be actuated by either manual means such as the rotatable screw 28, or by suitable automatic timing means, one type of which is shown at 3t); The enclosure bellows 47 shown is preferably of the type wherein the spring of the bellows itself normally biasesthe contacts 48 and 49 to a circuit interrupting position.

One bellows end wall 48a engages the manually adjustable stop screw 28, the other bellows end wall 49a yieldingly engages a cam 34. through a suitable linking or force transmitting means 50 and the wall thus is linked to the motor means 30. The force transmitting connection 50 between the cam 34 and the bellows 47 com; prises an axially elongated shaft 50b which is mounted insuitable bearings 51 with one end of the shaftdisposed in bearing engagement with the cam 34. A cup-shaped member 50a is mounted on the other end of shaft 5% and is adapted to surround and retain a portion of the bellows enclosure 47 as shown. Interposed between the bottom portion of the cup-shaped member 50a and the bellows end wall 48a is a coiled compression spring 52 which yieldingly biases the shaft 51 into engagement with the cam 34. The spring 52 together with the inherent spring of the bellows 47 also biases the other end wall 48a into engagement with the adjustable stop screw 28. Thus, upon suitable movement of cam 34 or movement of set screw 28, contacts 48 and 49 are mechanical- Iy moved between circuit completing and circuit interrupting positions. v

In the control of low power circuits employing a thermoelectric generator or the like, a change in contact pressure provides a change in the resistance at the contacts While they are in physical engagement. This change in resistance may be sufficient to effect the controlling change in the low power current flow through the contacts 48 and 49. Due to the fact that thermoelectric voltage is relatively minute, arcing of the contacts does not take place and thus a snap acting contact change of the current flow through the contacts may be had while the contacts are in physical engagement, the contacts do not have to be in physical engagement at all times and under all conditions.

The contact actuating cam 34 is disposed intermediate the ends of a shaft 32 and is suitably mounted thereon for movement therewith. The shaft 32 is provided with suitable bearings such as 33 and 33a with one end extending outwardly for coaction with a suitable knob 40 as will be later explained. The bearing 3311 may have as; sociated therewith a low frictional resistance and dust sealingO-ring 33b. The other end of shaft 32 is formed with suitable gear means 72 fixedly mounted at the extremity, the latter being adapted to engage the automatic timing means 30 for actuation thereby as'will now be described.

The condition responsive constant speed motor or electromagnetic step by step timing mechanism 30 is operable to turn contact actuating cam 34 and comprises a frame member 74 which is generally U-shaped in side view as shown most clearly in Figure 2. The frame member 74 has a pair of spaced irregularly shaped upstanding portions of arms 74a and 74b and has an inter;

- mediate portion which affords a support for permeable electromagnetic core 58. An energizing winding or coil 60 is wound on core 58 one end being grounded at 55 the other end being connected in circuit with the thermoelectric generator 20 as by conductors 21 and 21b. The pole face is formed with a lug portion 58a which extends to the left as shown in Figure 1. A stop screw 61a is threadably mounted in the lug 58a and extends upwardly through a suitable aperture in armature 62 for mac tion with a contact carrying strip 61 for purposes as will later be described. The aperture in the armature is larger than the stop screw, the walls thereof preferably never touching said, screw. The armature 62 is pivotally mounted upon the upstanding frame arm 74a as by pin 62a, and is movable between attracted and retracted positions with respect to the pole face 58b on core 58. A coil tension spring is anchored at one end to the armature 62 and at the other end to a suitable lug in the frame arm 74a as shown, said spring biasing the armature away from the pole face of the electromagnet 58.. The armature carries a set screw 59, a low resistance electrical contact member 63 and a small U-shaped permanent magnet 57, the purpose of each of which will appear hereinafter.

Insulatably mounted on a suitable upper lug of frame arm 74a is a resilient electrically conductive magnetically permeable contact carrying arm 61 which carries electric contact member 64, said contact member, like contact 63, preferably being of a corrosive resistant low resistance metal, for example gold. The contact 64 is positioned for engagement with the contact 63, and the permanent magnet 57 is positioned for coaction with the resilient contact arm 61 in a manner to be hereinafter described. Intermediate the ends of the upstanding frame arm 7411, a lug portion 740 extends to the left as shown in dot and dash line in Figure 2. The lug portion 74c is formed with an aperture having a suitable bearing surface for engaging shaft 32 which extends therethrough. An elongated ratchet or lever arm 66 is disposed next to the frame arm 74b and formed with an aperture at one end which loosely surrounds shaft 32 which acts as a pivotal bearing surface for said arm 66. The ratchet arm end opposite from the pivotal end extends to the right as shown in Figure 2 for engagement with one end of the set screw 59 which is fixed on the armature 62 for purposes as will be later described. Intermediate of the ends of ratchet arm 66 is a tension spring 67 one end of which is fixedly attached to the ratchet arm 66, the other end of which is fixedly attached to upstanding frame portion 74d. The tension spring 67 biases the arm 66 in an upwardly direction as shown in Figure 2. A large peripheral toothed ratchet wheel 68 may be loosely disposed on shaft 32 which forms a suitable axis therefor, said wheel being disposed between the gear means 72 and the ratchet arm 66. The relative- 1y smaller gear means 72 'is formed with a plurality of Further, as is most clearly shown in Figure 2, ratchet wheel 68 and gear means 72 are unidirectionally related so that gear means 72 may move in a clockwise direction relative to ratchet wheel 68 without attendant movement of the latter for purposes to be later described. A stop pawl 70 is mounted upon frame lug 74d and is so disposed so as to coact with the spaced teeth on ratchet Wheel 68 preventing movement of the latter in a counterclockwise direction but permitting clockwise movement of said' ratchet wheel. A third spring loaded pawl or detent 69' is mounted on movable ratchet arm 66 and is so disposed so as to coact with teeth of ratchet wheel 68 whereby movement of arm 66 in turn causes movementof ratchet wheel 68 in a clockwise direction only. Thus, as shown in Figure 2, downwardly movement of ratchet arm 66 causes clockwise movement of ratchet wheel 68, gear means-72 and shaft 32.

Unitary reset-timeset means 41 is provided for both moving the holding armature 37 into engagement with the holding electromagnet 35 and for adjustably determining the time cycle of the device 9. The resetting portion of the unitary reset-timeset mechanism comprises the reset button 40 which extends outwardly of the casing for manual engagement. The button or knob 40 is formed with a keyed bore 42 which is adapted to surround one end of the stem 32 with a pin 32a preventing separation of said stem and knob. The pin 32a is adapted to slide in the keyed portion of the bore 42 upon rectilinear movement of said knob while preventing relative rotational movement therebetween. A coil compression spring'43 is interposed between the underside of the knob 40 and the bearing 33 for biasing said knob in an outwardly direction. The portion of knob 40 disposed within casing 10 is preferably beveled for coaction with the rounded head of reset stem 44. The reset stem 44 is disposed substantially laterally of the shaft 32 and extends through a wall 80 with the inner end thereof adapted to engage valve disc 13 upon movement of the stem 44 to right as viewed in Figure 1. A coiled compression spring 81 is interposed between the head of stem 44 and the wall 80 to bias the reset stem head into engagement with the beveled surface of knob 40. A flow interrupter disc 82 is mounted on stem 44 for coaction with seat 83 to prevent all flow of fluid to the main burner 8 upon inwardly movement (to the right as viewed in Figure 1) of reset stem 44. A lost motion connection between the stem 44 and disc 82 is provided by shoulder means 85 and a coiled compression spring 84. The spring 84 is interposed between wall 80 and flow interrupter disc 82 to bias said flow interrupter disc against the shoulder means 85 and affords seating of the disc 82 upon seat 83 while permitting relative movement of stem 44 through disc 82 for engagement With disc 13. It is thus seen that inward reciprocatory movement of knob 40 of the unitary reset-timeset means 41 causes resetting of holding means 22 While preventing fuel flow to the main burner 11.

The timesetting portion of the unitary reset-timeset means 41 comprises a pointer 49a on knob 40 which coacts with a suitable calibrated dial 40b, the latter may be marked on the casing 10 as shown in Figure 1. Rotation of pointer 40a by rotation of knob 40 causes simultaneous, through rotation of stem 32, rotation of cam 34 which controls the position of contacts 48-49 of circuit controlling means 24 through the linking force transmitting means 50. The circuit controlling means 24 in turn controls energization of the holding or operator means 22. It will be seen in the following description of the operation of the device that depression of knob 40 is operable to reset the holding means 22 and rotation thereof is operable to control the time interval of energization of the holding means 22.

Operation To start the device 9 in operation, assume the following initial conditions: Valve disc 13 engaging seat 15 and preventing all fuel flow to both burners 8 and 12, control contacts 48 and 49 in circuit interrupting position, and timing motor contacts 63 and 64 in circuit making condition. To start the device in operation, pointer 40a is aligned as desired with the suitably calibrated dial 4% by a clockwise rotation of knob 40. Pin 32a in keyed bore 42 transmits the rotary movement of knob 40 to shaft 32 which in turn positions cam 34 to any one of the plurality of positions allowing contacts 48 and 49 to be in a circuit completing position. The dial 40b may be calibrated to indicate a position corresponding to the amount of time it will take cam 34 to move to a position allowing contacts 48 and 49 to interrupt the circuit to the holding means 22.

i To safely ignite burner 12, reset knob 40 is then manually depressed causing a downward movement along shaft 32 so that the beveled surface 45 engages the exterior rounded end of the flow interrupter stem 44 which in turn 83 to interrupt flow of fuel to the main burner 8. The

inner end of stem 44 then engages the under side of disc 13, which by way of armature stem 38 positions armature 37 in engagement with the pole faces of holding magnet 35. The valve disc 13 is thus positioned away from seat 15 allowing fuel to flow to pilot outlet port 17a and supply pipe 17 for ignition. After ignition of the pilot burner 20, the manual pressure on the reset button 40 may be removed and the resetting parts will return to the position shown in Figure 1.

With the pilot burner 12 ignited, the thermocouple 20 produces a thermoelectric current which flows in the electrical circuit shown in Figure 1 through the conductors 21, 21a, through coil 36, and contacts 48 and 49, to a suitable ground 54 and back to the generator 20. Another leg of the circuit branches off of conductor 21 at 21b to be in parallel relation with the circuit through coil 36. In the second part of the circuit the current flows through the conductor 21b, through conducting arm 61, through contacts 64 and 63, through winding 60, thence to a suitable ground 55 and back to the generator 20 'via a ground circuit such as the casing 10. Thus ignition of the pilot burner causes the thermoelectric generator 20 to be energized which in turn simultaneously energizes winding coil 36 of the holding means and winding coil 60 of the constant speed motor means. Energization of winding 36 causes armature 37 and hence valve disc 13 to be retained in a flow-permitting position against the bias of spring 39 when moved thereto by the reset means 40. The parts will remain in the cooked attracted relation shown in Figure 1 until such time as said winding 36 is deenergized.

When the timing electromagnet afforded by coil 60 and core 58 is energized, the armature 62 is attracted toward the pole piece 58b and moves toward said pole piece against the bias of spring 65. As the armature 62 so moves the armature screw 59 simultaneously rotates the lever or ratchet arm 66 in a clockwise direction, thus causing the pawl 69 to rcengage the tooth periphery of ratchet wheel 68 and rotate the latter with said ratchet arm.

During the attractive movement of the armature 62 the permanent magnet 57 holds the contacts 64 and 63 in engagement and thereby flexes the resilient contact arm 61. Before the armature 62 engages the pole piece 58b, however, the outer end of the contact arm 61 engages the set screw 61a, and further inward movement of the armature after said engagement pulls the contacts 63 and the magnet 57 away from the contact 64 and the resilient arm 61 respectively. Contact arm 61 is thus permitted to return to its retracted unfiexed position. At the same time disengagement of the contacts 63 and 64 interrupts the flow of energizing current and deenergizes the electromagnet. The armature 62 thereupon begins retractive movement under the bias of spring 65, and the lever or ratchet arm 66 moves counterclockwise with such retractive movement under the bias of spring 67. Ratchet wheel 68 does not move in the reversed direction with the lever 66 however, because such movement is prevented by the spring loaded pawl or detent 70. Thus, as the ratchet lever 66 moves counterclockwise during retraction of the armature, the pawl 69 moves into engagement with the next peripheral tooth of the ratchet wheel 68.

Deenergization of the coil 60 releases the armature 62 and causes contacts 63 and 64 to reengage to reeenergize electromagnet, and the permanent magnet 57 simultaneously magnetically reengages the contact arm 61 to effect of spring loaded detent 73. Accompanying the movement of shaft 32 is the movement of cam 34 which, through the force transmitting linking means 50, removes the bias uponv enclosure 47 to allowoontacts 48 and 49 to'move the circuit interrupting relation under thespring of the bellows itself. The time lapse necessary for moving the camv 34 to a position allowing interruption of the circuit to the holding means 22 is determined by the initial positioning of cam 34 by rotation of the reset knob 40. The unidirectional connection between the gear 72 and the ratchet wheel 68 permits relative movement therebetween which affords a setting of the cam 34 as desired.

Upon contacts 48' and 49 moving into circuit interrupting relation, the circuit through the holding electromagnet 36 is interrupted releasing armature 37 which causes disc 13 to move into flow-preventing relation with respect to the fuel to both of the burners. Upon the out-age of the pilot burner 12, the thermoelectric generator 25) ceases to generate current and the constant speed motor means 30 is in turn deenergized. It is apparent that outage of the pilot burner from any cause will deenergize both electromagnets so that the operation of the device will always-be of a safe nature.

Although a specific embodiment of the invention has been shown and described, it is with full awareness that many modifications thereof are possible. The invention therefore is not to be restricted except insofar as is necessitated by the appended claims.

What is claimed as the invention is:

1. In a timing control device for fluid fuel burning apparatus including main and pilot burners, valve means adapted to be disposed in the path of fluid fuel to both of said burners, said valve means being biased to flow-preventing and movable to flow-permitting position with re spect to the fluid flow, electromagnetic holding means operable when energized to hold said valve means in flowperrnitting position against said bias when moved thereto, thermoelectric generating means in circuit with said holding means and adapted to be responsive to the heat of fuel burned at one of said burners for energizing said holding means in response to burning of said fuel and for deenergizing said holding means in response to outage of said burner, electroresponsive timing means also connected in circuit with said thermoelectric generating means, said timing means comprising a constant speed motor means, circuit controlling means, and cam means driven by said-motor means, said cam means controlling said circuit controlling means for deenergization of said holding means at one position and to permit energization of the latter at another position, unitary reset means cooperating with said valve means and said timing means, rectilinear movement of said reset means being operable to reset said holding means for movement of said valve means to flow-permitting position, and rotary movement of saidreset means being adapted to selectively position said cam means in any of a plurality of positions each of which bear a timed relation to the position of said circuit controlling means causing deenergization of said holding means, wherefore said valve means will be released for movement toward flow-preventing position upon outage ofsaid one burner and upon movement of said cam means'by saidmotor means to its said'one position to provide safe time controlled fuel flow to both said burners.

2. In a timing control device for fluid fuel burning apparatus including main and pilot burners, flow control means for said burners biased to a first and movable to a second position with respect to the fluid iiow, holding means operable to hold said'fiow control means in its. second position against said bias when moved thereto but incapable of effecting movement of said flow control means to itssecond position, thermoelectric. generating means for energizing said'holdin'g means, timing means also connected in circuit'with said thermo'electric generating means, said timing means comprising a constant speed motor means, and circuit controlling means, under the control thereof, said circuit controlling means affording deenergization of said holding means at one position and permitting energization of the latter at another position, unitary reset-timeset means cooperating with said flow control means and said timing means, one movement of said reset-timeset means being operable to reset said holding means and move said flow control means to its second position, and a second movement of said reset-timeset means being adapted to selectively set said timing means, wherefore said fio-w control means will be released for movement toward its first position upon deenergization of said thermoelectric generating means or upon actuation of said circuit controlling means to said one position by said timing means.

3. Time controlled device for fluid fuel burning apparatus comprising, a valve member movable to open and closed positions and adapted to be disposed to control the fuel flow to a burner, means biasing said valve toward closed position, releasable holding means releasable inresponse to a predetermined unsafe condition and operable responsive to a predetermined safe condition to hold said valve member in open position when moved thereto but incapable by itself of elfecting movement of said valve member against the bias of said biasing means, settable timing means operatively associated with said holding means and operable to effect release of said holding means after a selected predetermined time lapse following setting, and unitary reset-timeset means cooperable with said valve member, holding means and timing means and operable to reset said valve member to open position against the bias of said biasing means and into holding cooperation with said holding means, said resettimeset means also affording setting of said timing means initiating operation thereof for said selected predetermined period, said valve member being thereafter released by said holding means for movement to closed position and safety shut-off of the fuel flow to said burner responsive to said unsafe condition and also responsive to expiration of said predetermined period.

4. In a timed controlled device for fluid fuel burning apparatus including a burner, control means adapted to be disposed to afford safety shut-off control of the flow of fluid fuel to said burner, said control means having first and second positions, means biasing said control means toward said first position, manually resettable operator means responsive to a predetermined condition for holding said control means in its second position when reset thereto, but incapable of effecting movement of said control means to said second position against said biasing means, settable timing means associated with said operator means operable to deactivate said operator means after a selected predetermined time lapse following setting, and reset-timeset means cooperable with said control means, operator means and timing means and operable to reset said control means to said second position and into holding cooperation with said operator means, said reset-timeset means also affording selective adjustrnent of the time interval of said timing means.

5. In a timed controlled device for fluid'fuel burning apparatus including a burner, control means adapted to be disposed to control the flow of fluid fuel to said burner, said control means having fiow permitting and flow-preventing positions, manually resettable operator means adapted to be responsive to a predetermined condition for holding said control means in its flow-permitting position when reset thereto, but incapable of effecting movement of said control means to flow-permitting position, timing means operatively associated with said control means for preventing fuel flow to said burner after a variable predetermined time lapse, and reset-timeset means cooperable with said control means, said resettable operator means and said timing means, one movement of said reset-timeset means being operable to reset said control means to flow permitting position and to reset said operator means, and another movement of said reset-timeset means afiording selective adjustment of the time interval of said timing means.

6. In a timed controlled device for fluid fuel burning apparatus including a burner, valve means adapted to be disposed to control the flow of fluid fuel to said burner, said valve means having closed and open positions, manually resettable holding means adapted to be responsive to the heat of burning fuel at said burner for holding said valve means in its open position when reset thereto, but incapable of eifecting movement of said valve means to its open position, timing means operatively associated with said valve means for selectively terminating the fuel flow to said burner after a variable predetermined time lapse, and reset-timeset means coopenable with said valve means, holding means and timing means, rectilinear movement of said resetetimeset means being operable to move said valve means to open positionand reset said holding means, and rotational movement of said resettimeset means aifording selective adjustment of the time interval of said timing means.

7. In a time controlled device for fluid fuel burning apparatus including main and pilot burners, control means adapted to be disposed to control the flow of fluid fuel to both said burners, said control means having first and second positions, means biasing said control means toward its first position, energy source means adapted to be associated with at least one burner for response to the heat of burning fuel thereat, manually resettable operator means energizable by said energy source means for holding said control means in its second position when reset thereto, but incapable of effecting movement of said control means to its second position, timing means operatively associated with said control means for selectively preventing fuel flow to at least one burner after a variable predetermined time lapse, flow interruption means operable to prevent fuel flow to at least one burner during resetting of said operator means, and reset-timeset means coopenable with said flow interruption means, operator means, control means and timing means, one movement of said reset-timeset means being operable to move said control means to its second position and reset said operator means while assuring shut ofi of fuel to at least one burner, said reset-timeset means also afiording selective adjustment of the time interval of said timing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,318,801 Ray May 11, 1943 2,375,569 McCarty May 8, 1945 2,467,944 Munson Apr. 19, 1949 

